## Core Concept
Sterilization of media containing serum or other heat-sensitive components requires methods that do not involve high temperatures, as these can denature proteins or destroy the biological activity of the serum. Filtration is a commonly used technique for achieving sterility in such cases.

## Why the Correct Answer is Right
The correct answer, **B. Filtration**, is right because filtration allows for the removal of microbial contaminants from heat-sensitive materials like serum without exposing them to high temperatures. This method uses filters with pore sizes that are small enough to block bacteria and other microorganisms, ensuring the sterility of the serum.

## Why Each Wrong Option is Incorrect
* **Option A:** Autoclaving involves high-pressure steam and is used for sterilizing materials that can withstand high temperatures. However, it is not suitable for serum or other heat-sensitive materials because the high temperature can cause denaturation of proteins.
* **Option C:** Radiation can be used for sterilization but is more commonly applied to products that are not suitable for heat or filtration methods. It's not typically used for serum due to potential damage to the serum components.
* **Option D:** Ethylene oxide gas sterilization is used for heat-sensitive equipment but is less commonly used for liquid media like serum due to the potential for residues and the need for careful handling.

## Clinical Pearl / High-Yield Fact
A key point to remember is that when working with biological materials like serum, **filtration** is a crucial technique for maintaining the integrity and sterility of the material. This is particularly important in cell culture and vaccine production, where the quality and sterility of the serum are critical.

## Correct Answer: B. Filtration